JP3345446B2 - Molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to preforming curved concrete elements for use in the construction of arch structures.

[0002] As can be seen from Japanese Patent Application No. 62-9196, it is well known to construct arch structures consisting of a number of rib-like elements of preformed concrete arranged along the length of the structure. ing. These elements are
Arranged in first and second rows, each element is held at its base on an individual undercarriage (footing).
Also, the elements of the first row engage with the elements of the second row at the apex of the structure. The concrete element is preformed using a device consisting of a curved convex formwork surface. Formwork surface, a number of formwork members interconnected in a hinged manner,
Provided by supporting from below with a number of vertical supports (posts) that can be adjusted in height and spacing. The forming apparatus has the advantage that a variable curvature (overall) can be imparted to the formwork surface in order to reuse the forming apparatus to preform elements of different curvatures.

In conventional devices, the change in curvature is achieved by relatively rotating the form members at the hinged interconnect. The individual formwork members themselves do not bend or flex to change the curvature. Therefore, the inner wall of the arch element formed by the surface of the formwork is composed of a series of straight portions close to a curve, but a continuous curve is desired in some situations. this is,
This can be achieved by providing a flexible formwork wall and bending to the required curvature. However, to provide a form wall that is sufficiently rigid to retain its shape when concrete is applied, and to make the form wall follow a large curvature without causing structural damage or permanent strain With problems.

In accordance with the present invention, there is provided an apparatus for preforming curved concrete elements for use in arch construction. This device consists of a formwork with an adjustable curvature wall that can accept uncured concrete for forming longitudinally curved concrete elements, and a device for adjusting the curvature of the formwork wall. Become. Therefore, the concrete elements having different curvatures can be formed by reusing the apparatus. There, the formwork wall comprises a first flexure member and a second flexure member which resiliently bend in the longitudinal direction before being fixed to each other, so that the formwork comprises the first and second members fixed together. The wall has a preset curvature.

[0005] By forming the formwork wall with a preset curvature, the curvature can be increased as needed without exceeding the elastic limits of the materials of the first and second members. On the other hand, when the form wall is in an initial straight state, a large curvature cannot be achieved without exceeding the elastic limit. Thus, in the present invention, the form wall can be adjusted according to the required large or sharp curvature without causing structural damage or permanent distortion, so that the curvature is significantly different. The device can be reused to form concrete elements. Also, the curved concrete element is provided with a smooth finish. This is because the formwork wall is adjusted by bending or bending according to the required curvature.

[0006] For the first member of the form wall, for example, a form such as a plate can be used. Also, the second
As the member, a reinforcing bar such as a reinforcing body extending in the longitudinal direction of the plate can be used. Desirably, there is a pair of second members in the form of spaced parallel reinforcing bars. The first member and the second member can be formed of a suitable material, such as steel, which can be elastically curved, and can be fixed to each other by welding. In a preferred method of pre-curving the first member and the second member, the first member and the second member are positioned so as to horizontally straddle between two supports, such as a wood-grinding table, and the load is further lowered by a weight and Add vertically. In this state, the members are tack-welded to each other, then the weight is removed, and the members are continuously welded in the longitudinal direction and fixed to each other. In this way, the second member fixed to each other and the formwork wall composed of the second member have a predetermined curvature. There is a slight tendency for the first and second members to recoil back and extend straight when the weight is removed, but generally the degree of recoil is not critical.

[0007] The formwork wall can be further stiffened by a stiffening member such as a gusset that is disposed longitudinally and perpendicular to the second member. These members are desirably fixed to the first member in the form of, for example, a plate by welding.

[0008] The adjusting device can be constituted by a number of longitudinally spaced adjusting elements whose length can be adjusted to adjust the curvature of the form wall. The adjusting element can rotate relative to the formwork wall,
It can move longitudinally relative to the support. A longitudinal movement of the adjusting elements does not mean that they twist with respect to the support. Therefore, deformation of the adjusting element can be avoided. Preferably, a longitudinally extending support is provided for the adjusting device. In that case, the adjusting element can maintain a vertical relation to the longitudinal support during its adjustment. The adjusting element can use the form of a threaded rod which is secured to the support by at least one nut so that it can be moved axially. It is desirable to provide a pair of nuts on both sides of the support. The nut shall be rotatable to move each threaded bar in the axial direction to adjust the curvature of the form wall.

When a support extending in the longitudinal direction is provided on the adjusting device, a straight support may be used. However, in some cases, because the preset form wall has a large curvature, a support that is not straight but has an angle that can follow the aforementioned preset curvature may be desired. The length of the adjusting element or other adjusting device can be so minimized that problems such as buckling under concrete pressure do not occur.

[0010] The longitudinal length of the formwork wall may substantially correspond to the length of the curved concrete element to be molded. However, it may be desirable to provide a plurality of longitudinally adjacent formwork walls, as the length of the concrete element may be 10 m or more. This makes it easier to transport the device using materials that are already available. For example, two or three formwork walls each having a length of 4 m can be used. A preferred embodiment comprises a plurality of formwork walls that are longitudinally adjacent with their longitudinal ends aligned to form a continuous formwork surface. A separate longitudinal support can be provided for each form wall adjustment device. This is again to facilitate transportation. To properly adjust the individual curvatures to avoid discontinuities on the formwork surface,
Special adjustment of the adjusting device may be required at the longitudinal end of the formwork wall. Thus, in a preferred embodiment, at least one longitudinal end of the form wall is adjustable in length and rotatable not only with respect to the form wall but also with respect to the longitudinal support. An adjustment element is provided. In this way, the adjusting element can be provided close to the longitudinal end of the form wall so that proper adjustment can be made while rotating to a position beyond the end of the longitudinal support.

The arch structure related to the present invention tends to have a maximum curvature near the vertex. Therefore, when molding concrete elements forming such a structure using a plurality of longitudinally adjacent formwork walls, the formwork walls forming the vertices of the concrete elements have the greatest curvature. Let For this reason, it is desirable that the preset curvatures of the formwork walls adjacent in the longitudinal direction are different from each other. By doing so, each formwork wall can be made to more accurately correspond to the final curvature which is a guide for adjustment.

The desired curvature of the formwork wall can be obtained by measuring or adjusting the adjusting device with preset values.
However, it is desirable that the device is provided with a template (in which the form wall can be adjusted) that defines the required curvature. The template can be formed of, for example, wood.

If the desired curvature of the formwork wall has been achieved using the adjusting device, it is advantageous to produce a plurality of concrete elements with that curvature without further adjustment. Accordingly, it is desirable that the apparatus include a device for separating the form wall from the curved concrete element without adjusting the curvature of the form wall. For example, the longitudinal support can be pulled apart with the adjusting device and the formwork wall. In a preferred embodiment, the traction device is comprised of a plurality of longitudinally spaced traction devices. If the longitudinal support is fixed with a traction device while the molding process is in progress, it is desirable to have one or all devices oriented in one direction different from the traction direction after the completion of the molding process . Therefore, it is desirable that at least one traction device has a function of adjusting the direction of traction. For example, a hinge-type coupling means is applied to the longitudinal support for this purpose.

In a preferred embodiment, the formwork walls are arranged vertically so that the edges of the longitudinal sides of the formwork walls are stable on a floor slab or the like while the forming process is in progress. Therefore, it is desirable that the present apparatus is provided with a lifting device for lifting the formwork wall before towing. If a lifting device is provided, the undesirable operation of dragging the formwork wall on the floor slab can be avoided.

Although the formwork walls may be used to provide an upwardly arched, formwork surface for receiving uncured concrete from below, the apparatus includes a side wall for receiving uncured concrete. It is desirable to form a pair of formwork walls that are vertically arranged while providing an interval in the direction. The final upper and lower surfaces of the concrete element are:
It is formed by contacting spaced formwork walls. Therefore, smooth both surfaces can be obtained without performing hand finishing. Further advantages are as follows.
Since the formwork walls keep the concrete from the side, there is no need to support the entire weight of the concrete-thus reducing the weight of the equipment and lowering the cost. The operator does not need to work below or at a very high position on the partially raised formwork (usually the width of the concrete element or the height at the location of the molding process is 1.25 m). The concrete element is formed with its side edges down and can be stored in its place. Therefore, there is no need to rotate the element before the concrete has completely hardened.

The present invention uses the device as described above,
A method is also provided for preforming curved concrete elements for use in arch construction. The invention also applies to concrete elements formed using this device.

A preferred embodiment of the present invention will be described by way of example and with reference to the accompanying drawings.

It will be appreciated that various drawings are schematically depicted and, in some cases, parts of the molding apparatus have been omitted to more clearly show other parts. Furthermore, the drawings are drawn to various scales.

Referring to FIG. 1 and FIG. The forming apparatus 1 comprises two longitudinally adjacent form walls 2 forming the inner surface of a cavity 3 in the form apparatus, and a form apparatus arranged laterally spaced from the inner form wall 2. Consists of two longitudinally adjacent formwork walls 2 which form the outer surface of the cavity 3 of FIG.

Each mold wall 2 has an adjusting device 4 comprising a number of adjusting rods 5 arranged at intervals in the longitudinal direction.
Is provided. As shown in FIG. 2, one set of adjustment rods 5 is located near the top of the form wall and another set is located near the base of the form wall. The adjusting rod 5 is rotatably coupled at its front end to the formwork wall 2 (as described below in connection with FIGS. 8, 9 and 10), and is axially adjustable and can remain longitudinal. (See below in connection with FIGS. 9 and 10).

The adjusting rods 5 provided at each end of the longitudinal support 6 cannot slide in the longitudinal direction, but are instead connected by a pivot type connecting device 14 (see FIGS. 11, 12 and 13). And as described below).
In this way, the adjusting rods 5 at the end portions can be connected close to the longitudinal end portions of the respective formwork walls 2 so that the curvature can be appropriately adjusted in the region of these end portions. A coupling device 15 is provided between adjacent longitudinal ends of the form wall (as described below in connection with FIGS. 14 and 15).

At the respective longitudinal ends of the cavities 3 in the forming apparatus, partitions 16, 17 are provided for closing the cavities (to form the final cutting edge of the concrete element). The partition 16 is described later with reference to FIG. 20).

Each longitudinal support 6 is provided with a pair of support legs 7 spaced apart in the longitudinal direction. The support legs 7 corresponding to the inner form wall 2 are bolted to the floor, and the support legs 7 corresponding to the outer form wall 2 are
Mounted on the traction device 8. Therefore, a pair of traction devices are provided for each form wall, spaced apart in the longitudinal direction. Each traction device is
It has an upper beam 9 which is slidably held on a lower beam 10 bolted to the floor. The upper beam 9 is slidable in the axial direction by a threaded rod 11 projecting rearward through a threaded hole in a non-rotating boss 12. The rotation of the bar causes an axial movement, which is transmitted to the upper beam 9 which can be active on the lower beam 10. The support legs 7 corresponding to the outer formwork walls 2 are connected to the respective longitudinal supports 6 by means of vertical hinges 13 as shown in FIG. 1, so that the direction of traction can be adjusted (FIGS. 16 to 16). 19, as described below in connection with 19).

Above the inner form wall 2, there is provided a template 18 which defines the desired curvature when adjusting the form wall (shown in FIG. 2, but for the sake of 1 is omitted). This template
It is also useful as a walking path for workers. At the base of the cavity 3 in the molding device, a further template 19 is provided so that the curvature of the formwork wall at the edge of the base can be adjusted precisely. For this purpose, the template 19 is provided with an inner edge 20. The template also has an outer edge 21 so that the desired curvature of the lower edge of the outer form wall 2 can be determined. Regarding the adjustment of the curvature of the upper edge of the outer form wall 2,
This will be described later with reference to FIG.

The configuration of each form wall 2 will be described with reference to FIGS. The formwork wall 2 is composed of a flexible plate 22 using a steel plate having a thickness of 0.25 inch (6.4 mm), a length and a height of 4 m and 1.25 m, respectively. After bending to the required curvature, such a plate can be returned to its original position without structural damage or permanent distortion. However, to increase the rigidity of the skin and ensure stability under concrete pressure,
A pair of upper and lower horizontal reinforcements 23 are required. As the reinforcing member, for example, a flat steel bar having a height of 125 mm and a thickness of 12 mm can be used. The reinforcement is
It is fixed to the flexible plate 22 by continuous welding 24.

When the formwork wall 2 consisting of the flexure plate 22 and the horizontal stiffener 23 fixed to each other is used in the initially straight forming apparatus 1 and bent to the most severe curvature required, the inside of the stiffener is Stress exceeds its elastic limit. Therefore, before welding the horizontal reinforcing member 23 to the flexible plate 22, the form wall is bent in the longitudinal direction so that the stress in the horizontal reinforcing member is below the elastic limit at the maximum curvature. As shown in FIG. 5, in order to achieve this, a portion close to the longitudinal end of the flexible plate 22 (steel plate) and the horizontal reinforcing member 23 is cut from below with a wood grinder 25, 26 so as to secure a pre-bending width △. Support and apply a downward load 27 to the center. Under these conditions, the horizontal reinforcing member 23 and the flexible plate 22 are tack-welded to each other, and the downward load 27 is removed to facilitate the work, thereby forming a continuous weld. Removing the downward load 27,
There is a slight tendency for the formwork wall 2 to return and straighten in reaction, but this is not particularly critical. When the recoil returns, the formwork wall already has a curvature from the pre-bending process. Therefore, preparation for using the form wall in the molding apparatus 1 is completed.

FIG. 6 shows how a formwork wall 2 can be formed into a curved concrete element for an arch structure having a span in the range of about 4.6 to 15.2 m and a height of 2.4 to 6.1 m.
Is used. The large arch shown in FIG. 6 requires three longitudinally adjacent formwork walls 2 each having a length of 3-4 m, while a medium sized arch requires each length 2 to 4 m are required. In addition, a small arch requires one formwork wall 2 having a length of 1 to 4 m. Note that the curvature of each arch is greatest near the top. Thus, when forming a concrete element that requires more than one formwork wall 2 along its length, it is desirable to use formwork walls having different preset curvatures. Therefore, a large arch is formed by a pair of second mold walls 2B and a first mold wall 2A having a larger preset curvature, and a medium arch is formed by the second mold walls 2B and 2B. It is formed by the first mold wall 2A having a large preset curvature. Also, the small arch is formed by a single form wall of type 2A. For example, a first form wall of type 2A has a pre-bend width 450 of 450 mm (see FIG. 5), whereas a second form wall 2B has a pre-bend width of 200 mm.

Referring to FIG. The vertical rigidity of the formwork wall 2 is determined by the number of vertical stiffening gussets welded to the flexible plate 22.
This is reinforced by longitudinally spacing 28.

The adjusting device 4 for adjusting the curvature of the form wall 2 will be described in detail with reference to FIGS. The adjusting device 4 corresponding to each formwork wall 2 consists of a number of adjusting rods 5 which are arranged at intervals in the longitudinal direction. For example,
Adjustment rods are arranged at 400 mm intervals. Each adjusting rod 5 is threaded and its front end is fixed to a coupling assembly 30 by a nut 29. The coupling assembly is pivotally connected to the horizontal stiffener 23 via a coupling pin 31 so as to be rotatable about a vertical axis. The threaded adjusting rod 5 is connected to the longitudinal support 6 at the rear end. The longitudinal support 6 comprises a pair of back-to-back U-shaped sections 32 with a vertical spacing between the two U-shaped sections for the adjustment bar 5 to pass through. The U-shaped section 32
In this state, it is fixed by the support legs 7. On both sides of the U-shaped section a pair of sliding plates 33 with adjustment nuts 34
Is provided. By properly rotating the adjustment nut 34, the adjustment rod 5 moves axially with respect to the U-shaped section 32. Therefore, by adjusting the length of the adjusting rod 5 between the longitudinal support 6 and the form wall 2, the curvature of the form wall can be effectively adjusted. Lock nut 35
The adjustment rod 5 is fixed at a final position for performing molding.

FIG. 10 shows a longitudinal support 6 during curvature adjustment.
3 shows a preferable state in which the adjustment rod 5 can be moved in the longitudinal direction. In this figure, the formwork wall 2 and the adjusting rod 5
Are shown by dotted lines, and their adjusted states are shown by solid lines. When the adjustment is completed,
Is moving longitudinally along the line X of the longitudinal support 6 so that the vertical relationship to the longitudinal support is maintained. Such longitudinal movement can be achieved by the U-shaped section 32.
The movement of the adjusting rod 5 in the gap between them and the longitudinal sliding movement of the sliding plate 33 along the U-shaped section 32 are made possible.

FIGS. 11 to 13 show a pivot type coupling device 14 used for the adjusting rod 5 at the longitudinal end of the longitudinal support 6. Each coupling device comprises a rotary pin 37 provided with a threaded hole 38 for receiving the threaded adjustment rod 5. Rotating pin 37
Is rotatable with respect to the U-shaped section 33 so that the adjustment rod 5 can rotate about the vertical axis of the rotary pin 37. The adjustment of the adjustment rod 5 in the axial direction becomes effective by its rotation.

The coupling device 15 between the ends of the longitudinally adjacent formwork walls 2 is shown in detail in FIGS. Each formwork wall 2 has an apex angle section
36 are welded. The bolt 39 and the nut 40 fix the vertical section 36 to each other and are locked by the tack weld 41 in this state. Four cylindrical bars 42 so that they can function as spacers between the vertical sections 36
Is provided.

FIGS. 16 to 18 show an outer form wall 2 from a bent concrete element formed in a cavity 3 in a forming apparatus.
Shows how are separated. The longitudinal support 6 corresponding to the form wall 2 having the largest curvature is provided with a curved portion 43 so as to be closer to the curvature of each form wall. As a result, the adjusting rod 5 does not have to be excessively long to cause buckling. While the molding process is in progress, it is desirable to vertically couple the support legs 7 to a portion of the longitudinal support 6 to ensure proper bracing and support for the form wall 2. This state is shown in FIG.

In order to be able to simultaneously pull the entire outer frame (consisting of two longitudinally adjacent outer form walls 2) without adjusting the curvature of the outer frame, at least the legs 7a are connected by the vertical hinges 13. Longitudinal support 6
Is combined with Therefore, the leg can be rotated as shown by the arrow in FIG. 16 and brought to the position shown in FIG. Then, as shown in FIG. 18, the traction device provided for each outer support leg 7 (see FIG. 2) can be operated to pull the entire outer framework away from the molded concrete element.

FIG. 19 shows the lift mechanism 44 directly attached to the form wall 2. A number of lifting mechanisms 44 are used, each provided in harmony with the support legs 7. That is, a plurality of lift mechanisms are combined to form a lift device for the entire form wall 2. Each lift mechanism 44 has an upper assembly 45 connected to the formwork wall 2 by a vertical hinge 46 and a lower assembly 47 connected to the upper assembly 45 by a horizontal hinge 48.
The lower assembly 47 supports a rotating wheel 49, and the relative pivoting movement between the upper and lower assemblies is enabled by an adjustment screw 50. When the adjusting screw 50 is lowered, the lower assembly 47 is pivoted downward, so that the form wall 2 is lifted off the floor.
This is done when it is desired to pull the form wall 2 after the molding has been completed. With this method, the form wall can be moved on the floor without dragging. During the fine adjustment of the form wall 2, the rotating wheel 49 is raised so that the form wall is stabilized on the floor. The vertical hinge 46 is for rotating the lift mechanism 44 in accordance with the direction of traction.

FIG. 20 shows a bulkhead for closing the end of the cavity 3 in the forming device which forms the leading edge of the bent concrete element. The septum 16 is provided with a curved portion 51 for forming a concrete element with a concave groove (which will be horizontally extended when used). The bulkhead is also provided with a portion 52 for forming the edge of the concrete element with a chamfer.

FIG. 21 shows a top spreader 53 for positioning the top edge of the outer form wall 2 with respect to the top edge of the inner form wall 2 (see FIG. 2) which is positioned with respect to the template 18. Is shown. The spreader is
It also serves to maintain the proper spacing between the top edges of the form wall 2 under concrete pressure. Spreader 53
Has a bridging member 54 between the adjusting screw 55 and a pin 56 that fits in the cylindrical member 57.

When used, the molding apparatus 1 is provided with the form wall 2
Is adjusted to match the curvature defined by the templates 18,19. After the appropriate adjustment is completed, the end walls 16 and 17 are positioned and the form wall 2 is oiled. Then, the reinforcing bar is attached, and the uppermost spreader 53 is fixed. Next, the concrete is poured into the cavity 3 in the forming apparatus and shaken. The top edge of the concrete element, which in use becomes a side edge, does not touch the formwork surface and is finished using a trowel. When the concrete is fully cured, the bulkheads 16 and 17 are released and the top spreader 53 is removed. The support legs 7 corresponding to the outer formwork wall 2 are arranged in parallel with each other. The formwork wall is lifted by the lift mechanism 44. Furthermore, the adjacent formwork wall 2
The entire outer framework is towed without adjusting the connection between them, while maintaining the curvature of the entire outer framework. A traction device 8 is used to separate the outer framework from the concrete element. The concrete element is removed using inserts cast on the exposed side edges. Using the traction device 8, the outer framework is returned to its original position and the support leg 7 is reset to its original position so that it is perpendicular to the longitudinal support 6. The partitions 16, 17 and the top spreader 53 are returned to their original positions so that further elements can be molded.

By providing new templates 18, 19 depending on the required design, the forming device can be easily adjusted to form concrete elements of different curvatures. Various members of the molding apparatus 1 can be disassembled and transported. Moreover, those members can be assembled easily and quickly. Workers do not need to work at very high levels or under formwork. Manual finishing is only required on one edge of each concrete element. The concrete element has smooth upper and lower surfaces that are uniformly (continuously) formed. The concrete element can be stored with one side down. This is the position where the concrete is formed, so that unnecessary stress can be avoided when the concrete is not fully cured.

[Brief description of the drawings]

FIG. 1 is a plan view of a molding apparatus according to the present invention.

FIG. 2 is a sectional view of a molding apparatus.

FIG. 3 is an elevation view of a formwork wall of the molding apparatus.

FIG. 4 is an end view of a formwork wall.

FIG. 5 is a plan view of the formwork wall when a pre-bending process is in progress.

FIG. 6 is a plan view showing different combinations of formwork walls.

FIG. 7 is an end view of the formwork wall, showing a vertical stiffening gusset secured to the formwork wall.

FIG. 8 is a plan view showing a state in which the form wall and a device for adjusting the curvature of the form wall are combined.

FIG. 9 is a longitudinal sectional view of the connection state in FIG. 8 and also shows the connection state of the adjusting device and the longitudinal support.

FIG. 10 is a plan view of a formwork wall, an adjusting device, and a longitudinal support.

FIG. 11 shows a longitudinal section of a modified version of the coupling device between the adjusting device and the longitudinal support used at the longitudinal end of the support.

FIG. 12 is an elevation view in the direction of arrow XII shown in FIG. 11;

FIG. 13 is a plan view in the direction of arrow XIII shown in FIG. 11;

FIG. 14 is a plan view showing the coupling device between the longitudinal ends of two adjacent formwork walls.

FIG. 15 is an elevational view of the coupling device shown in FIG. 14;

FIG. 16 is a plan view of the forming apparatus at different stages of the traction process of the form wall forming the outer forming surface of the bent concrete element.

FIG. 17 is a plan view of the forming apparatus at different stages of the traction process of the formwork wall forming the outer forming surface of the bent concrete element.

FIG. 18 is a plan view of the forming apparatus at different stages of the traction process of the form wall forming the outer forming surface of the bent concrete element.

FIG. 19 is an elevation view showing the traction wheel and a state where the traction wheel is coupled to the formwork wall.

FIG. 20 is a plan view of a partition wall used between two laterally spaced walls to close the gap at the longitudinal ends of the walls.

FIG. 21 is an elevational view of an uppermost spreader provided at the uppermost portion of two formwork walls spaced apart in the horizontal direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forming device 2 Form wall 3 Cavity in a forming device 4 Adjusting device 5 Adjusting rod 6 Longitudinal support 7 Supporting leg 8 Traction device 14 Pivot type coupling device 23 Horizontal reinforcement 30 Connection assembly 44 Lift mechanism

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Peter W. Canada, El 5C.2 X3, Avongate Drive, Mississauga, Ontario 2471 (56) References JP-A-63-303706 (JP, A) JP-A-60-6409 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B28B ^7/ 00-7/46

Claims (11)

(57) [Claims] An apparatus for preforming a curved concrete element for use in the construction of an arch structure, said adjustable curvature being capable of receiving uncured concrete to form a longitudinally curved concrete element. And a device for adjusting the curvature of the formwork wall, whereby the device can be reused to form concrete elements of different curvatures, the formwork wall comprising A first flexure member (22) functioning as a first flexure member and a second flexure member (23) fixed to the first flexure member to reinforce the first flexure member. The second flexible members can be elastically curved in the longitudinal direction before being fixed to each other, the first flexible member is a form plate, and the second flexible member is a supplementary member for reinforcing the form plate. An apparatus, wherein the form wall is a strong bar and the form wall comprising the first and second flexure members secured to each other is provided with a preset curvature. 2. The apparatus according to claim 1, wherein said adjusting device comprises a plurality of longitudinally-spaced adjusting elements whose length can be varied when adjusting the curvature of the formwork wall. A device in which the element is rotatable with respect to the formwork wall and longitudinally movable with respect to its support. 3. Apparatus according to claim 1, comprising a support extending in the longitudinal direction corresponding to the adjusting device, wherein the support extending in the longitudinal direction is not straight but at an angle. The device according to the preset curvature of. 4. Apparatus according to claim 1, comprising a plurality of longitudinally adjacent formwork walls, the longitudinal ends of the formwork walls defining a substantially continuous formwork surface. A device that is aligned so that it can be formed. 5. The apparatus of claim 4, wherein the preset curvatures of the longitudinally adjacent formwork walls are different from each other. 6. Apparatus according to claim 1, comprising a template defining a preferred curvature, wherein the curvature of the form wall is adjustable with respect to said template. 7. Apparatus according to claim 1, comprising a device for towing the formwork wall away from the curved concrete element without adjusting the curvature of the formwork wall. apparatus. 8. The device of claim 7, wherein the traction device comprises a plurality of longitudinally-spaced traction devices, at least one of the traction devices being capable of adjusting the direction of traction. An apparatus having 9. The apparatus according to claim 7, wherein the vertical arrangement of the form wall stabilizes the edges of the longitudinal sides during the course of the molding process, so that the form wall can be removed before towing. A device consisting of a device for lifting. 10. Apparatus according to claim 1, comprising a pair of vertically arranged and laterally spaced formwork walls for receiving uncured concrete. . 11. A method for preforming a curved concrete element for use in the construction of an arch structure, using the apparatus according to claim 1.